"The incident is a symptom of the growing atmosphere of Islamophobia in the US," the communication director CAIR group says. The council also urged US mosques to increase their security following the incident.
The US Federal Bureau of Investigation on Saturday took over the investigation of an early-morning bombing of a mosque outside Minneapolis that caused no injuries.
Bloomington police said the bomb damaged only the imam's office at the Dar Al Farooq Islamic Center and worshippers extinguished the blaze before firefighters arrived.
#FBIMinneapolis working to determine who caused the explosion and why.— FBI Minneapolis (@FBIMinneapolis) August 5, 2017
#FBIMinneapolis asks for the public's help. Please send info to 1-800-Call-FBI— FBI Minneapolis (@FBIMinneapolis) August 5, 2017
"A witness saw something being thrown at the imam's office window from a van or truck before the blast," Asad Zaman, Director of the Muslim American Society of Minnesota, said at a news conference. The mosque's executive director Mohamed Omar added that the vehicle immediately sped away.
The predominant Somali mosque, like many other mosques around the country, has received threatening calls and emails, Omar told the Star Tribune.
"It was 5 am (0900GMT)," he said. "The whole neighbourhood was calm. People were supposed to be sleeping, that's how peaceful this should be. I was shocked to learn this happened."
Several other area religious leaders joined members of the mosque on Saturday to express support.
The Council on American Islamic Relations (CAIR), announced a $10,000 reward for information leading to the arrest and conviction of the attacker.
It's national office also urged mosques and Islamic centres nationwide to increase security.
"The incident is a symptom of the growing atmosphere of Islamophobia in the US," the group's communication director, Ibrahim Hooper, said. "Because whenever you look at what would be a possible motive in this kind of case, it seems that Islamophobia would be a main type of motivation that you would look at."
Hooper said rewards have been successful in the past to receive information leading to an arrest.
"Because often they brag to people and friends, their relatives, that they've done this and they are proud of it. Then somebody eventually, because of the incentive of the reward, offers information to the police and they are arrested," he added.
Anti-Muslim incidents have risen sharply in the United States over the past year, according to a review by the Council on American-Islamic Relations.
A analysis by CAIR earlier in May this year, found 2,213 anti-Muslim bias incidents in the United States last year, up 57 percent from 2015.
The council urged US mosques to increase their security following the Bloomington incident.